Dazzle camouflage of warships was adopted by the U.S. Navy during World War II, following research at the Naval Research Laboratory. Dazzle consists in painting obtrusive patterns on vertical surfaces. Unlike some other forms of camouflage, dazzle works not by offering concealment but by making it difficult to estimate a target's range, speed and heading. Each ship's dazzle pattern was unique to make it more difficult for the enemy to recognize different classes of ships. The result was that a profusion of dazzle schemes were tried, and the evidence for their success was at best mixed.